1. Field of the Invention
The present invention relates generally to mass transfer between immiscible fluids to the absorption and desorption of gases in liquids, and specifically to sparging dissolved gas from a monomer containing liquid. More particularly, the present invention relates to the continuous removal of dissolved oxygen from a monomer solution by agitating the liquid with a countercurrent flow of compressed nitrogen. The invention has specific application in the field of industrial polymerization.
2. Background Discussion
Frequently, liquid monomer solutions which are polymerized on an industrial scale are saturated with air for storage and shipping in order to prevent the monomer from polymerizing prematurely. The oxygen present in such air saturated monomer solutions plays a critical role in preventing premature polymerization from occurring; and accordingly, said oxygen must be substantially removed from the solution before a well controlled polymerization reaction can be accomplished.
In the prior art, oxygen is frequently removed from monomer solutions by a sparging operation wherein the liquid monomer solution is agitated by the passage of compressed nitrogen. In batch operation, prior art sparging is generally accomplished by placing the liquid monomer solution in a large tank where it is contacted with compressed nitrogen entering the tank through a diffuser located in the bottom of the tank. There is an inherent inefficiency in batch sparging due to the mixing of sparged and unsparged liquid.
In continuous prior art sparging, nitrogen flows into the bottom of a gas-liquid contactor such as a packed column or a bubble plate column and upward through downflowing monomer solution which is continuously admitted at the top of the column. This method has the disadvantage that the column is potentially subject to fouling due to the gradual buildup of polymer in the completely sparged regions of the column. The present invention provides a means of efficiently and countercurrently contacting the aforementioned sparging gas with the aforementioned monomer solution under circumstances where no structural components are required for effective dispersal.